Method of and apparatus for releasing stuck pipe



Oct. 26, 1965 F. B. NELSON I 3,213,941

' METHOD OF AND APPARATUS FOR RELEASING STUCK PIPE Filed Feb. 1, 1962 3 Sheets-Sheet 1 INVENTOR. I2 FRED B. NELSON,

ATTORNEY.

Oct. 26, 1965 F. B. NELSON 3,213,941

METHOD OF AND APPARATUS FOR RELEASING STUCK PIPE Filed Feb. 1, 1962 3 Sheets-Sheet 2 5 o v Q 56 INVENTOR. FRED B. NELSON,

ATTORNEY.

Oct. 26, 1965 F. B. NELSON 3,213,941

METHOD OF AND APPARATUS FOR RELEASING STUCK PIPE Filed Feb. 1, 1962 3 Sheets-Sheet 3 FRED B. NELSON,

ATTORNEY.

United States Patent 3 213 941 METHOD or AND Ar rAiiArus non RELEASING STUCK PiPE Fred B. Nelson, Chickasaw, Ala., assignor to Norman A. Neison Filed Feb. 1, 1962, Ser. No. 170,696 4 Claims. (Cl. 166-46) This invention relates to the releasing of pipe which has become stuck in a well bore during the drilling or completion of the same.

In the drilling of wells, and particularly in the drilling of wells for the production of oil and gas, it is customary to make use of a rotary drilling bit, which is attached to the lower end of a tubular drilling string for rotation therewith in the well bore, and through which suitable drilling fluid is circulated downwardly and allowed to flow upwardly through the annulus surrounding the string, to carry away the cuttings formed, and for other purposes.

The drilling string usually employed in the rotary drilling process includes a string of pipe of substantially smaller external diameter than the diameter of the well bore and a number of drill collars of heavier construction and larger external diameter than that of the drill pipe above and to which the drilling bit is attached.

During the drilling of wells with equipment of this kind, the drilling string often becomes stuck in the well due to any of a number of conditions, such as the formation of key seats in the bore, the caving in of the formation or the settling of mud, cuttings, or the like, during periods when circulation of the drilling fluid is suspended. Under such conditions it may then become impossible either to continue the drilling or remove the string, making it necessary to carry out expensive and time consuming washover, side-tracking, or other remedial operations.

Moreover, in recent times, it has been learned that sticking of the string is often caused by a condition commonly referred to as differential pressure sticking in which the pressure of the fluid in the well exceeds the pressure in the surrounding formation. This condition may exist when the formation is a permeable one so that at locations where the pipe is in contact with the Wall of the bore the differential pressure tends to hold the pipe against the wall, thus increasing the resistance to rotational and longitudinal movement of the pipe in the well. Sticking of the string under these conditions is greatly increased when the drill collars rest against the wall of the bore due to the larger area of contact at such locations. Such sticking of the pipe may be greatly increased in the event that it should become necessary to temporarily discontinue movement of the string or suspend circulation of the drilling fluid.

Various expedients have been employed heretofore in an endeavor to prevent the sticking of or effect the release of drill pipe which has become stuck in the bore, such as the spotting of oil in the annulus surrounding the pipe, pumping fluid out of the annulus, the use of spirally grooved drill collars, or by including in the drill string assembly a packer which may be set to seal off the annulus at a desired location by suitable manipulation of the string and means for opening the string to allow the pressure in the annulus to be reduced when the packer has been set to reduce the differential pressure exerted on the pipe.

These conditions and problems affecting the sticking of drill pipe also arise with other well pipe, such as casing pipe or liner pipe.

The present invention has for an important object the provision of a method for releasing a pipe string which has become stuck in the well bore due to such differential pressure sticking and which may be also used as an aid in the releasing of a string which has become stuck from other causes.

Another object of the invention is to provide a method for releasing differential pressure stuck pipe in a well by the reduction of the pressure of fluid in the annulus surrounding the pipe to reduce the force exerted on the pipe which tends to hold the pipe in contact with the wall of the well bore.

A further object of the invention is the provision of a method for producing a water hammer effect in a column of fluid in a well bore at a location to create a pressure wave in the column about the exterior of a pipe string whereby the force tending to hold the string in contact with the wall of the well bore may be reduced.

Another object of the invention is to provide a method for releasing stuck pipe in a well bore by alternately restricting and opening the pipe to interrupt the downward flow of circulating fluid therethrough, whereby a water hammer effect is produced which exerts a downward force on the pipe and creates a reduction in the pressure in the annulus surrounding the pipe to reduce the differential pressure sticking effect of the fluid on the pipe.

Another object of the invention is the provision of apparatus for releasing a pipe string which has become stuck in a well bore embodying means incorporated in the pipe string, which is designed to substantially close and open the string in response to variation of the pressure differential of the circulating fluid across said means so as to produce a water hammer effect on the string and in the column of fluid surrounding the same tending to release the string.

A further object of the invention is to provide apparatus for use in releasing a string which has become stuck in a well bore, which includes an internal seat in the string and valve means designed for coaction with the seat to substantially close the same, and which may be substantially closed and opened by variation of the flow rate of the circulating fluid in the string to create a down ward water hammer effect on the string and a reduction in pressure in the fluid surrounding the string to reduce the force exerted on the string tending to hold the string in contact with the wall of the well bore.

A still further object of the invention is the provision of apparatus for releasing a stuck string which is of simple design and rugged construction and which may be initially incorporated in the string to be carried therein throughout the duration of the drilling operation or which may be readily inserted in the string and operated to release the string upon the occurrence of sticking.

A further object of the invention is to provide apparatus of the type referred to which, when incorporated in the string does not interfere with the circulation of drilling fluid during normal procedure of the drilling operation, but which may readily be operated to release the string upon the occurrence of sticking.

The above and other important objects and advantages of the invention may best be understood from the following detailed description, constituting a specification of the same, when considered in conjunction with the annexed drawings, wherein-- FIGURE 1 is a vertical, central, cross-sectional view, on a reduced scale, of a well and drilling mechanism associated therewith illustrating the invention and showing somewhat schematically a drilling string positioned in the well bore and the apparatus by which the drilling operation is carried out;

FIGURE 2 is a cross-sectional view, on an enlarged scale, taken along the line 2-2 of FIGURE 1, looking in the direction indicated by the arrows;

the wall.

FIGURE 3 is a longitudinal central, cross-sectional view of a preferred embodiment of the fluid pressure controlled valve means of the apparatus of the invention, the valve being shown in its open position;

'FIGURE 3A is a fragmentary, side elevational view of the upper end portion of the device of the invention as illustrated in FIGURE 3, showing one form of the grapple or fishing apparatus employed for retrieving the valve mechanism from the well pipe, the grapple being shown in its catching position in the fishing head and in position to hold the valve in open position;

FIGURE 3B is a fragmentary, side elevational view,.

partly broken away and partly in cross-section, illustrating a somewhat modified form of the valve member of the invention as illustrated in FIGURE 3;

FIGURE 4 is a cross-sectional view, taken along the line 44 of FIGURE 3, looking in the direction indicated by the arrows;

FIGURE 5 is a fragmentary, vertical, central, crosssectional view of a somewhat different form of the fluid flow control mechanism of the invention, the mechanism being shown in closed position; and

FIGURE 6 is a View similar to that of FIGURE 5, illustrating a further modification of the fluid flow control mechanism of the invention, the mechanism being shown in its open condition.

Referring now to the drawings in greater detail, the invention is illustrated in connection with its use with well drilling equipment of the usual type, such as that shown in FIGURE 1, having a drilling string generally designated 10, positioned for rotation in a well bore W, and which carries at its lower end a drilling bit 12, of conventional design. The drilling string 10 is of the usual make-up including a string of pipe 14 of somewhat Smaller external diameter than that of the bore W and which is connected at its lower end to one or more drill collars 16 whose external diameters are somewhat larger than that of the pipe 14. The drilling bit 12 is, of course, substantially larger in diameter than the drill collars to provide an annulus A about the drilling string to permit suitable drilling fluid to be circulated downwardly through the string and upwardly through the annulus.

The usual equipment for rotating and manipulating the drilling string is provided at the well head and suitable means is also provided for controlling the circulation of the drilling fluid, such as the mud pump 18 whose discharge line 22 is connected in communication with the upper end of the string under the control of a valve 24, and whose inlet is connected in communication with a source of drilling fluid such as the mud pit 26 through an intake line 28. A drilling fluid return line 30 is connected in communication the annulus A and discharges into the pit 26.

The mud pump 18 has a by-pass line 32 connected to its discharge outlet, through which drilling fluid may flow back to the pit 26 under the control of a suitable valve 34.

In carrying out the drilling of a well with equipment of this kind, the drilling string 10 is rotated with the bit 12 in engagement with the bottom of the bore W, while circulating drilling mud downwardly through the string and upwardly through the annulus A to carry away cuttings and cool the bit. During such drilling operations, it frequently occurs that the drill collars 16 or some other portion of the string lies in contact with the wall of the bore, as shown in FIGURES 1 and 2, and under some conditions, such as when the bore passes through a relatively permeable formation, such as that shown at P, the pressure of the fluid in the annulus A may exceed the pressure of fluid in the formation, so that a force is exerted on the string tending to hold the string against Under such conditions, the string may be held against the wall of the bore with suflicient force to cause sticking of the string in the bore so that it becomes impossible to rotate the String or move the same longitudinally. Such sticking of the string due to the difference between the pressure of fluid in the bore and that in the surrounding permeable formation is commonly known as differential pressure sticking, or sometimes as wall sticking of the string, and may be particularly great when the drill collars 16 are in contact with the wall of the bore at a permeable formation due to the increased external surface area presented by the drill collars, as illustrated in FIGURE 2.

It is for the purpose of preventing the above described differential pressure sticking and for releasing the string when such sticking has taken place, that the present invention is primarily intended.

At times the method of the invention may be carried out by employing the above described drilling equipment, to prevent differential pressure sticking of the drilling string or to release the same in the event that such sticking should take place. In carrying out the method of the invention with this equipment, circulation of the drilling fluid is maintained and rotation of the drilling string is continued, if possible. With the equipment thus operating, the valve 24 of the well fluid supply line 22 from the mud pump 18 may be momentarily closed to interrupt the circulation of the drilling fluid to produce a water hammer effect, whereupon a reduction in the pressure in the supply line will occur immediately beyond the valve in the direction of flow of the fluid, which will cause a pressure wave at .a reduced pressure to be propagated downwardly through the column of liquid in the drilling string and upwardly through the annulus about the string. Due to the fact that the column of fluid from the valve 24 downwardly through the drilling string and upwardly in the annulus about the string is continuous, the pressure wave thus produced will be very rapidly transmitted through the entire column and back again therethrough to the valve, causing a momentary reduction in the pressure in the annulus, resulting in a corresponding reduction in the differential pressure exerted on the string, tending to hold the string against the wall of the bore, so that the string may then be moved away from the Wall. 'By alternately opening and closing the valve 24 successively, reduced pressure waves may be propagated in the annulus as often as desired to prevent the sticking of the string to the wall of the bore, or to produce a condition under which the string may be released, if stuck.

For the purpose of more effectively carrying out the method of the invention, it is preferable, however, to incorporate in the drilling string suitable means for opening and closing the string at a desired location to simultaneously produce a downward water hammer effect on the string and a reduced pressure Wave in the annulus, whereby a downward force may be exerted on the string during the reduction in the differential pressure which is holding the string against the wall of the bore to more effectively release the string. A preferred embodiment of such means is illustrated in FIGURES 3 and 4, the device being shown in FIGURE 3 in position in the string and in open condition preparatory to the carrying out of a releasing operation.

The device of the invention, illustrated in FIGURES 3 and 4 comprises an outer tubular housing 38, whose upper end is externally threaded, as indicated at 40 for the attachment thereto of an internally threaded centering plug 42, formed with external, peripherally spaced, outwardly extending wings 44 positioned for sliding engagement with the surrounding wall of one of the drill collars 16, to hold the device centered therein, and to provide clearance between the housing and drill collar through which drilling fluid may flow downwardly through the string. At its lower end, the housing 38 is internally threaded as indicated at 46 for the attachment thereto of the upper end of a by-pass element 48, which is shaped to provide a passageway 50, through which drilling fluid may flow downwardly through the drilling string. At its lower end, the by-pass element 48 is formed with a downwardly tapering external face 52, positioned to seat on an internal, tapered annular seat 54, formed in the drilling collar 16 to close the seat when the device is in position in the drill collar. A valve member 58 is movably disposed in the by-pass element 48 for longitudinal movement therein and is provided with a bevelled external face 60 positioned for engagement with the seat 56 to close the element upon downward movement of the valve and to open the seat upon upward movement of the valve. The valve member 58 is connected to a valve stem 62 which is slidably extended upwardly into the housing 38 through an upwardly thickened annular portion 64 of the by-pass element 48. Suitable sealing means such as the O-rings 66 and 68 are disposed in annular grooves provided for the same in the portion 64 in position to form fluid tight seals between the housing and by-pass element and between the by-pass element and the valve stem 62. The stem 62 is connected at its upper end to an internal piston 70, slidably mounted in the housing and which carries suitable means, such as the O-ring72 positioned to form a seal between the piston and the internal surface of the housing.

Yieldable means, such as a coil spring 74 surrounds the stem 62 in the housing or barrel 38, which is seated at one end on the piston 70 and at the other end on the internally thickened portion 64 of the by-pass element 48 to yieldingly urge the piston upwardly in the housing. The piston 70 has a stem 76 connected thereto which is slideably extended upwardly through the centralizer 42 and which carries at its upper end a fishing head 78.

The piston 70 is formed with an internal passageway 80 within which an internal valve seat 82 is formed, against which a valve 84 may seat to close the passageway against the upward flow of fluid therethrough. The valve 84 is yieldingly urged toward closed position, as by means of a coil spring 86, whereby the valve may open to permit the downward flow of fluid through passageway 80, but which holds the valve closed against the upward flow of fluid through the passageway. The piston 70 also has upper and lower lateral openings 88 and 90, respectively, the opening 88 being in communication with the interior of the housing above the piston and with the passageway 84) above the seat 82, and the opening 99 being in communication with the interior of the housing below the piston and with the passageway 80 below the valve seat 82, and the piston is also provided with control orifice passageways 92 through which fluid may by-pass the valve seat 82. Although two passageways 92 are shown, it is clear that only one may be used if desired by simply plugging the other.

It will thus be seen that the piston moves longitudinally in an annular chamber 94 formed between the internal surface of the housing and the external surfaces of the stems 62 and 76.

The housing has an internal longitudinal by-pass groove 96 in the lower portion of the chamber 94, beyond which the piston is located when the piston is in its uppermost position, and through which fluid may flow past the piston when the piston reaches a predetermined position in its downward movement.

A pressure equalizing piston 98 is slidably movable on the stem 76 in the chamber 94 above the piston '78 and is provided with suitable sealing means such as the O-rings 100 and 102 positioned to form seals between the piston and the housing and between the piston and stem 76.

In the event that some of the fluid in the chamber 94 should leak out, the equalizing piston 98 will be moved inwardly by the pressure of circulating fluid in the string entering the centralizer 42 through the passageway 110 so that the chamber is at all times maintained filled with fluid.

A coil spring 104 surrounds the stem 76 within the centralizer 42 which spring is seated at one end on an internal shoulder 106 in the centralizer and at the other end against the piston 98 to urge the piston downwardly in the chamber 94.

The centralizer 42 has an internally thickened portion 108 providing a central opening of somewhat larger diameter than that of the stem 76 to provide a passageway 110 through which fluid may flow into and out of the interior of the centralizer above the piston 98.

The by-pass element 48 is provided with a lateral opening 112 through which fluid may flow out of the chamber 94 in assembling the device, after the chamber has been filled with a suitable hydraulic fluid to allow the bypass element to be screwed into the housing.

The valve seat 54 may be formed in the drill collar 16 or some other part of the drilling string in any suitable manner, or may be formed in a connector member or sub 114, as shown in FIGURES 5 and 6 for connection into the string at a desired location.

In making us of the equipment illustrated in FIGURES 3 and 4, the by-pass element 48 is removed from the housing 38 and the chamber 94 is completely filled with hydraulic fluid, whereupon the by-pass element may be replaced, the excess fluid being allowed to leak out of the housing through the opening 112 until the seals 66 and 68 are in sealing position, whereupon the equalizing piston 98 will he moved against the pressure of the spring 104 until the by-pass element has been fully screwed into place to assure that the chamber 94 is entirely filled when the device is assembled.

The valve actuating piston 70 will then be held in its uppermost position in the housing by the spring 74, and the valve 58 will also be yieldingly held in open position, as illustrated in FIGURE 3.

With the device thus completely assembled, the complete assembly may be lowered into the string to position the same with the external bevelled face 52 of the by-pass element 48 in closing contact with the seat 54 of the string.

Under some conditions, it may be desirable to place the device in the string during the assembling of the string, in which case the seat 54 may be conveniently located in the lowermost one of the drill collars 16, or in the sub 114 by which the drilling bit is connected to the drill collars, so that the seat is located above and close to the lower end or the drilling string. Should it be desired to omit the device from the string when the same is being assembled, the string may be assembled with the seat 54 at the desired location, and the device may be lowered in the string at any convenient time by disconnecting the string at the well head.

When the device has been positioned in the string as described above, drilling fluid may flow downwardly through the string past the housing 38 and through the passageway 50 of the by-pass element 48, the valve 58 being open, so that circulation of the fluid through the string and upwardly in the annulus A in the usual manner may take place during the drilling operation.

During downward flow of the circulating fluid through the passageway 50, there will be a drop in pressure created immediately below the valve 58 which will cause the exertion of a downward force on the valve against the resistance of the spring 74, and in the event that the string should become stuck or should it be felt that diflerential pressure sticking of the string may be likely to occur, then the flow rate of the circulating fluid may be increased to increase the downward force on the valve 58 until th resistance of the spring 74 is overcome, whereupon the piston '70, stem 62 and valve 58 will move downwardly in the housing. During initial downward movement of the actuating piston 79 in the region above the internal groove 96, such downward movement will be additionally yieldingly resisted by the fluid in the housing which cannot flow upwardly through the seat 82 of passageway which is closed by the valve 84, but must flow through the small central orifice passageways 92. Thus downward movement of the actuating piston takes place slowly until the piston reaches the internal groove 96, whereupon fluid may then flow rapidly through the groove past the piston, and the piston will move downwardly suddenly to substantially close the valve 58.

Upon substantially closing of the valve 58 downward flow of the circulating fluid through the string will be reduced, causing a downward water hammer effect on the string which, due to the length of the fluid column above the valve may exert a great downward force on the string. At the same time the restricting of flow at the valve 58 will cause the pressure in the circulating fluid immediately below the valve seat 54 to fall momentarily to a very low value approaching zero, thereby creating a low pressure wave in the fluid which will travel rapidly upwardly through the fluid in the annulus A and return again downwardly therethrough. The low pressure wave thus produced results in a reduction in the pressure of fluid in the annulus about the drilling string so that the differential pressure tending to hold the string against the internal surface of the well bore is momentarily reduced and in some cases reversed and the string is prevented from sticking, or if stuck is released.

In the event that it is possible to lift the string so that the bit is out of contact with the bottom of the bore, the weight of the string may be used in addition to the water hammer effect of the flow reduction at the valve to cause the string to move to further assure the releasing of the string.

After the valve 58 has reached closed position, it may be quickly moved to the open position again by reducing the pressure of the circulating fluid above, whereupon the piston 70 will be quickly moved upwardly by the spring 74, the fluid in the chamber 94 flowing rapidly past the piston through the groove 96 and also downwardly through passageway 80 through the Valve seat 82 to allow such return movement. By thus repeatedly applying increased pressure to the circulating fluid above the valve 58 and then reducing such pressure, it will be apparent that the water hammer and reduced pressure wave effects may be repeated as often as desired without substantially interfering with the continuous circulation of the drilling fluid.

When desired the device may be readily retrieved from the string by the use of fishing equipment of the usual type, which may be engaged with the fishing head 78 in a well known manner.

A somewhat modified form of the invention is illus trated in FIGURE 313, wherein the valve member 58a is of the same general configuration as the valve member 58 previously described, but is provided with one or more passageways, such as that indicated at 59, through which restricted flow of fluid may take place from above the valve member to below the same when the valve is closed. By this arrangement, the circulation of fluid may be reduced upon closing of the valve to obtain the reduced pressure wave effect without completely interrupting the flow of fluid.

As illustrated in FIGURE 3A, the fishing equipment used for this purpose may take the form of a grapple 79 having spring fingers 81 at its lower end which are formed with inwardly thickened Portions 83, mediate their ends to provide upwardly facing shoulders positioned for engagement beneath the head 78 to connect the grapple to the head. The fingers 81 are shaped to be spread apart by engagement with the head 78 when the grapple is lowered over the head until the head is extended upwardly between the fingers past the shoulders 83, whereupon the fingers Will be snapped inwardly to hold the shoulders in position for engagement beneath the head to cause the head to be lifted up with the grapple in retrieving the valve mechanism. The fingers 81 may be somewhat elongated, as shown at 85 to position the lower ends of the fingers for engagement with the upper end of the centralizer 42 when the grapple is engaged with the head 78 to hold the valve 58 in open position when it is desired to resume circulation of the drilling fluid without actuating the flow interrupting mechanism. The grapple 79 may, of course, be attached 119 .2 Cable or other suitable means for retrieving the same, or may be connected to the lower end of a rod or weight to be lowered or dropped into engagement with the head 78 and centralizer 42 to hold the valve open without retrieving the valve assembly.

A somewhat different form of the apparatus of the invention is illustrated in FIGURE 5, wherein a valve member 116 of solid construction and generally cylindrical configuration is shown, which is formed with an external downwardly bevelled face 52' at its lower end positioned for closing engagement with the internal seat 54 of the string. The member 116 also has a fishing head 78' at its upper end and is of somewhat smaller external diameter than the internal diameter of the string.

The valve member 116 may be used to carry out the method of invention by inserting it in the string at the well head by any well known means, and allowing the member to move downwardly with the downwardly flowing circulating fluid. When the member reaches the seat 54' the downward flow of fluid in the string will he suddenly arrested to produce the above described water hammer and reduced pressure wave effects to release the string. The member 116 may also be lowered in the string 'by suitable wire line equipment by which the member may be manipulated to close and open the seat to repeatedly obtain the water hammer and reduced pressure Wave effects when desired.

A further modification of the apparatus of the invention is illustrated in FIGURE 6. The valve mechanism of this form of the apparatus takes the form of a tubular valve casing 118 having an external bevelled face 52 at its lower end which is engagea'ble with the inside seat 54 to close the same. The casing 118 has an annular valve seat element 122 threadably attached to its upper end which is formed with an annular valve seat 56' through which fluid may flow downwardly through the string. A valve member 53' is movably extended through the seat element 122, which member has a t-apered face 60 positioned for engagement with the seat 56' to substantially close the seat. The member 58 also has a stem 126 movably extended through the seat element and which carries a cross-member 128 on its lower end which is engageable with the inner end of the seat element to prevent the valve from becoming separated from the assembly. A fishing head 78" is also formed on the valve 58. The casing 118 has an internal upwardly facing shoulder 130 against which one end of a coil spring 132 is seated whose other end bears against the cross-member to yieldingly urge the valve toward open position. The casing 118 is of somewhat smaller external diameter than the internal diameter of the pipe string to allow the assembly to move downwardly readily in the string to engage the face 52" of the casing with the seat 54' to close the seat.

In making use of the valve assembly of FIGURE 6, the assembly may be placed in the string on the seat 54 upon initial assembly of the string, or lowered in the string from the well head. During the normal progress of the drilling operation, the valve 58' will be held open by the spring 132 to allow circulation of drilling fluid through the string when it is desired to perform a releasing operation, the flow rate of the drilling fluid may be increased until the pressure of the spring is overcome, whereupon the valve will close to produce a downward water hammer on the string and to cause a reduction in the pressure of fluid immediately below the valve to produce a low pressure wave in the annulus to release the differential pressure sticking of the string. Upon again reducing the pressure of the circulating fluid in the string above the valve the spring 132 will reopen the valve to permit circulation of the drilling fluid at normal circulating rate.

It will be apparent that by suitably adjusting the pressure exerted by the valve opening springs 132 or 74, the differential pressure at which the valves will be closed may be regulated as desired so that the valves can be rate and reopened by suitably reducing the pressure above the valves.

The invention may, of course, be employed for releasing drill pipe which has become stuck due to other causes than differential pressure sticking and may be used to produce a jarring action on the string for any desired purpose.

Although the preceding has been described in the light of a drilling operation using drill pipe, it is apparent that the methods and apparatus could be employed in conjunction with other types of pipe used in wells, such as casing, tubing and liners.

It will thus be seen that the invention provides an effective method and apparatus of simple design which may be used for the releasing of differential pressure stuck pipe or for other similar purposes.

The invention is disclosed herein in connection with certain steps of the method and specific embodiments of the apparatus employed in carrying out the same, but it will be understood that these are intended by way of example only and that numerous changes can be made in the contruction and arrangement of the parts as well as in the particular steps of the method, within the spirit of the invention and the scope of the appended claims.

Having thus clear-1y shown and described the invention, What is claimed as new and desired to secure by Letters Patent is:

1. In apparatus for use in releasing a pipe string stuck in a well bore, the combination with a body member adapted to be connected into a pipe string and having an inside seat through which a fluid may flow downwardly through the string and upwardly in the bore about the string, of a valve assembly in the string and including a housing shaped for engagement with the seat to substantially close the seat and having a passageway therethrough and an inside valve seat in said passageway through which fluid may flow through the string, a valve movably disposed in the housing for downward movement into and upward movement out of closing relation to said valve seat and yieldable means positioned for coaction with the valve and housing to yieldingly urge the valve in the housing away from said valve seat.

2. In apparatus for use in releasing a pipe string stuck in a Well bore, the combination with a body member adapted to be connected into a pipe string and having an inside seat through which a fluid may flow downwardly through the string and upwardly in the bore about the string, of a valve assembly movably disposed in the string and including a housing shaped for engagement with the seat to substantially close the seat and having a passageway therethrough and formed with an inside valve seat in the passageway through which fluid may flow through the string, a valve movably disposed in the housing for movement into and out of substantially closing engagement with the valve seat, yieldable means positioned for coaction with the valve and housing to yieldingly resist closing movement of the valve, said valve being movable to closed position against the resistance of said yieldable means when the downward pressure diiferential of the fluid across the valve exceeds a predetermined value to cause the fluid in the string above the valve seat to exert a downward force on the string and to open position upon the occurrence of a reduction in the pressure of fluid above said valve seat to cause such pressure diflFerential to fall below said value.

3. In apparatus for releasing a pipe string stuck in a well bore the combination with means forming an internal seat in the string-through which fluid may flow downwardly through the string and means movably disposed in the string for movement into and out of closing relation to the seat, of means adapted to be lowered into the string and shaped for coaction with said seat forming means and said movable means to lock said movable means out of closing relation to the seat.

4. The method of releasing a pipe string stuck in a well bore, which string is provided with an inside seat through which fluid is circulated downwardly through the string and upwardly in the bore about the exterior of the string, a valve assembly movably disposed in the string and including a housing shaped for engagement with said inside seat and having a passageway therethrough and formed with a valve seat in the passageway through which fluid may flow through the string, a valve movably disposed in the housing for movement into and out of closing engagement with the valve seat and yieldable means positioned for coaction with the string and said valve to yieldingly resist closing movement of the valve, which method comprises increasing the pressure of the fluid in the string to cause the valve to close against the resistance of said yieldable means to cause the fluid in the string above the seat to exert a downward force on the string and thereafter reducing the pressure of the fluid in the string above said seat to allow the valve to open.

References Cited by the Examiner UNITED STATES PATENTS 2,221,775 11/40 Boynton 166177 X 2,758,817 8/56 Bassinger 296 X 2,905,439 9/59 Martini 175-296 X 3,007,523 11/61 Vincent 166177 X 3,038,548 6/62 Brown 166-178 X BENJAMIN HERSH, Primary Examiner.

BENJAMIN BENDETT, Examiner. 

3. IN APPARATUS FOR RELEASING A PIPE STRING STUCK IN A WELL BORE THE COMBINATION WITH MEANS FORMING AN INTERNAL SEAT IN THE STRING THROUGH WHICH FLUID MAY FLOW DOWNWARDLY THROUGH THE STRING THROUGH WHICH FLUID MAY FLOW POSED ION THE STRIONG FOR MOVEMENT INTO AND OUT OF CLOSING RELATION TO THE SEAT, OF MEANS ADAPTED TO BE LOWERED INTO THE STRING AND SHAPED FOR COACTION WITH SAID SEAT FORMING MEANS AND SAID MOVABLE MEANS TO LOCK SAID MOVABLE MEANS OUT OF CLOSING RELATION TO THE SEAT.
 4. THE METHOD OF RELEASING A PIPE STRINK STUCK IN A WELL BORE, WHICH STRING IS PROVIDED WITH AN INSIDE SEAT THROUGH WHICH FLUID IS CIRCULATED DOWNWARDLY THROUGH THE STRING AND UPWARDLY IN THE BORE ABOUT THE EXTERIOR OF THE STRING, A VALVE ASSEMBLY MOVABLY DISPOSED IN THE STRING AND INCLUDING A HOUSING SHAPED FOR ENGAGEMENT WITH SAID INSIDE SEAT AND HAVING A PASSAGEWAY THERETHROUGH AND FORMED WITH A VALVE SEAT IN THE PASSAGEWAY THROUGH WHICH FLUID MAY FLOW THROUGH THE STRING, A VALVE MOVABLY DISPOSED IN THE HOUSING FOR MOVEMENT INTO AND OUT OF CLOSING ENGAGEMENT WITH THE VALVE SEAT AND YIELDABLE MEANS POSITIONED FOR COACTION WITH THE STRING AND SAID VALVE TO YIELDINGLY RESIST CLOSING MOVEMENT OF THE VALVE, WHICH METHOD COMPRISES INCREASING THE PRESSURE OF THE FLUID IN THE STRING TO CAUSE THE VALVE TO CLOSE AGAINST THE RESISTANCE OF SAID YIELDABLE MEANS TO CAUSE THE FLUID IN THE STRING ABOVE THE SEAT TO EXERT A DOWNWARD FORCE ON THE STRING AND THEREAFTER REDUCING THE PRESSURE OF THE FLUID IN THE STRING ABOVE SAID SEAT TO ALLOW THE VALVE TO OPEN. 